Add support for prefetching fields
This makes it possible to specify the fields that should be
prefetched as part of a getForFields query. Doing a prefetch on a
ReferenceProperty when it is known that the property will be
referenced in (almost all) entities is far more efficient than
doing the invididual fetches sequentially.
from django.conf import settings
from django.db import models
from django.db.models.fields import FieldDoesNotExist
class CurrentSiteManager(models.Manager):
"Use this to limit objects to those associated with the current site."
def __init__(self, field_name='site'):
super(CurrentSiteManager, self).__init__()
self.__field_name = field_name
self.__is_validated = False
def get_query_set(self):
if not self.__is_validated:
try:
self.model._meta.get_field(self.__field_name)
except FieldDoesNotExist:
raise ValueError, "%s couldn't find a field named %s in %s." % \
(self.__class__.__name__, self.__field_name, self.model._meta.object_name)
self.__is_validated = True
return super(CurrentSiteManager, self).get_query_set().filter(**{self.__field_name + '__id__exact': settings.SITE_ID})